Marrella was the first fossil collected by Charles Doolittle Walcott from the Burgess Shale, in 1909.[1] Walcott described Marrella informally as a "lace crab" and described it more formally as an odd trilobite. In 1971, Whittington did a thorough redescription of the animal. On the basis of its legs, gills and head appendages, he decided that it was not a trilobite, nor a chelicerate, nor a crustacean.[2]

Marrella-like organisms are found in other Cambrian deposits. They are known from sediments as late as the Devonian.[3]